In response to recent changes in life style, a trend toward soft and smooth household thin paper becomes apparent in users. Especially, in the filed of tissue paper, such a trend is significant.
In order to ensure flexibility, addition of a quaternary ammonium salt is known as disclosed in Japanese Patent Publication No. 3180916 (Patent Reference 1). Also as disclosed in Japanese Patent Publication No. 2806974 (Patent Reference 2), addition of a polysiloxane substance is known.
However, in order to impart flexibility to paper, if a softening agent is added so that the paper is soften, paper strength is decreased, thus, for example in the case of tissue paper, it easily tears in blowing a user's nose, in wiping off user's makeup.
On the other hand, in order to impart moist feeling to paper, addition of a moisture retention agent is known. In Patent Reference 3, water-disintegrable paper is proposed, which includes a moisture retention agent such as glycerin, diglycerin, low molecular weight polyethylene glycol or the like, a dry paper strength agent such as carboxymethyl cellulose sodium, starch or the like, and water soluble wax comprising polymeric polyethylene glycol.
However, the water-disintegrable paper does not have enough water-disintegrability to satisfy a level required as toilet paper. In addition to this, a use of a dry paper strength agent tends to damage flexibility of the paper.
[Patent Reference 1] Japanese Patent Publication No. 3180916
[Patent Reference 2] Japanese Patent Publication No. 2806974
[Patent Reference 3] Japanese Patent Publication No. 3454997